Method of producing a tow of filamentary material



Feb. 24, 1959 w. N. SELLERS 2,874,446

METHOD OF PRODUCING A TOW 0F FILAMENTARY MATERIAL Filed Nov. 4, 1955ATTORNE Y.

United States Patent E METHQD F PRODUCING .A TOW OF FILAMENTARY'MATERIALI William N. Sellers, Stamford, Conn assiguor to AmericanCyanamidCompany, New York, N. Y., ti-corporation of Maine Application November4,1955, Serial'No."544,847

8 Claims. '1.(Cl. 28- 72) mentary material, advantageously one comprisedof e polymer of acrylonitrile containing :a major proportion (preferablyat least 75%) by weight of acrylonitrile combined in the polymermolecule.

It was suggested prior to'my invention that certain "vegetable fibers(specifically cotton, hemp, jute, ramie and flax) and certainuncrosslinked thermoplastic .synthe'tic fibers (specifically viscoseand'acetate rayons, 'nylon, fibers :made .from condensation products of'terephthalic 'acid and glycol, and fibers :made from polyvinylidenechloride) be mechanically crimped while hot and'lthen immediately.crimp-setby cooling, While compacted undera substantiallyconstantpressure, in .a cooling zone of the same apparatus. Such amethod and apparatus for practicing the "same are described in, :forexample, =Rainard U. SrPatent No. 2,575,839.

vA'method of crimping and crimp-settinga tow of a .polyacrylonitrilefilamentary material is disclosed and claimed in thecopendingapplication of :Mario Sonnino, Serial No. 545,043, filedconcurrently with the present application. In the specific crimp-settingtechnique therein described by way-of example, the crimp is fixed bypassing the tow of synthetic'filamentary material through a so-calledJ-box or other suitable receptacle containing cold water. The cold'waterthatis take'nup by the tow (thereby forming a saturated'towymustsubsequently be removed by asqueezeroll or other-suitable device;

and therernoval of this entrained'wate'r may, undercer- 'tainconditions, "cause fiber entanglement and reduction of crimp amplitude.If no consideration be-givento the tow as a final product, thesqueeze'roll or equivalent 'device maybe by-passed and thecrimp-set'tow' may be'cut into staple while it contains approximately400% by weight of moisture. it is thennecessary to form'the cut stapleinto a blanket which must' be squeezed,'separated or r e-opened, andthen conveyed to a stapledryer for drying the cut staple.

The present invention hasas its primary object an improvement upon thecrimp-setting methods described above. Briefly described, theimprovement comprises continuously passin'g'a tow of a"polyacrylonitrile filamentary material, and more particularly onecomprised of a, polymer of acrylonitrile containing ta major proportionby weight of acrylonitrile combinedinthapolymer molecule, at atemperature of girom aboutv 150 ,E to

about 260 1 directly from :atow crimper, wherein it, has beenhot-crirnped mechanically, to a quenching-zone in which cooled .gas;(e.-g., cooled .air,,.nitrogen, flueigas, etc.) is circulated. The.towquenching-apparatus-oinso- Patented Feb. 124, 195% =-crimping apparatus,as a consequence act which the hot- "crimped tow is readily availablefor inspection prior to setting ofthe crimp therein and the practicaladvantages of which will be immediately apparent'to those skilled -'-inthe art. 'The hottow in relaxed state :is supported -on-a movingsupport, e. g., a continuously "moving-apron or screen formed of metalor other suitable material. This supportis preferably porous, e. g., bybeing provided with orifices or slots, or by the 'use of wire screening,so :as to facilitate the passage of the cooled gas through :the'thuslysupported tow. The supported, relaxed tow is ,passed "continuouslythrough the quenching zone. The t'e'mperature of the quenching zone andthe time the tow .is present therein are correlated so that the tow isat a temperature below 120 F., and preferably not higher than about 100.F., when it leaves the said zone.

The crimp-set tow, after it leaves the tow quencher, can be=cutintostaples, e. g., by means of centrifugal cut- .ters, and thencedried, opened and baled for shipment; or, alternatively, it can be driedin the form of tow, and .the dried tow then plaited'into a suitablecontainer for shipment as tow.

Byqnenching the hot-'crimped tow=in a separate cooling i'zo'ne while .ina'relaxed state in accordance with my invention, thereis fgreaterassurance of obtaining a more unirform'produ'ct since there is lesschance for physical damage to thecrimped tow. A uniform product is amatter .of iconsiderableipractical importance, not only from thefstan'tlpointiof d-ye'uniiormity butalso from the standpoint ofuniformity in mill processing and in enduses. Still :anothertreasonfortheimprovementin the quality of'the towzis duext'o theLfact 'thatit issubjected to less handling will .be-lapparentfrom theifollowin'gparagraph) while :it lie in a. condition or .state when "it .isirelatively sensitive to damage.

,As compared with processes that involve passage through water or othercooling fluid, or spraying with such fluids, the method of thisinvention eliminates such a :step. :As aresult, the number of subsequentprocess :steps is thereby :reduced and substantial :savings in operatingand. equipment costs are attained; furthermore, drying costs-also arereduced since .the moisture content'ofithe, towisreduced during itspassage through the tow quencher.

Another advantage of the -'invention is "the fact thatit :requires nolarge floor-areas, :orexpensive or specially constructed apparatus. inmarked contrast, the :equipmerit required to-practice the method'of theinvention is called tow quencheris separate and'distinct 'from thecompact, relatively inexpensive andtreadily available.

Still another advantage of the invention is the fact that it-obviatesiorminimizes filament entanglement, knot- 1ting,;etc., that occur or tendto occur if a'continuously moving, .hot-crimped, polyacrylonitrile .towor strand, While still hot, is exposed to blasts of .cold air or othergas sufficient to cool the tow'quickly and to. set the crimp.

The novel features'of theflinvention are set forth in theappended-claims. Theinvention itself, however, will be understood mostreadily from the following detailed description thereof when consideredin connection with the -faccornpanying drawing, which is illustrative ofthe invention, and in which:

.Fig. .l1is a cross sectional end view of one form of apparatus that canbe used in practicing the method of the invention, and showing the towon a. moving support thatcarriesitthrough theapparatus;

I 'Fig. 2 is a side-elevation and somewhat schematic view ofthe-apparatusillustrated in Fig. .1 and 'showing';the -to'w b'ein'gcarried through, 'andlcaving, the apparatus; "and a t "'FigjB is-a'perspective view of a portion .ofthemoving support shown in Figs. 1 and2, and of one means "for laying the tow upon the support end of apreferred manner in which the tow is laid or plaited upon the support.

Referring to the drawing, a crimped tow is led directly from a towcrimper (not shown), wherein it has been hot-crimped mechanically, to atow quencher 12. The tow is hot when it leaves the tow crimper, e. g.,at a temperature of from about 150 F. to about 200 F. and, moreparticularly, about 165 F. to about 195 F. The hot, crimped tow which isquenched in accordance with the present invention is a tow of syntheticfilamentary material, and more particularly a tow of polyacrylo nitrilefilamentary material, e. g., one comprised of a polymer of acrylonitrilecontaining a major proportion (advantageously at least 75%) by weight ofacrylonitrile combined in the polymer molecule. Crimped tows of apolyacrylonitrile filamentary material containing 50%, or less than 50%(e. g., as little as 35 or 40% by weight of acrylonitrile combined inthe polymer molecule are not precluded from treatment as hereindescribed in order to set the crimp with the same attendant advantagespreviously stated earlier in this specification.

The tow 10 enters the feed-in section 14- of the tow quencher 12 throughan opening 16 in the side wall 18 of the said section. The hot tow, asreceived from the tow crimper, is generally wet with water and maycontain, for example, from about 50% to about 150% by weight of water,based on the weight of the bone-dry tow. The tow passes between a pairof feed rolls comprising a lower roll 20 and an upper roll 22 whichlightly presses the tow upon the lower roll. From the pair of feed rollsthe tow passes through the plaiting tube 24, which is positioned abovethe continuously moving support 26 as shown. This plaiting tube lays thehot tow, while it is in a relaxed state, in a transverse, zigzag patternupon the said moving support, and is moved back and forth, as indicatedby the arrows 23, by means of conventional traverse mechanism (notshown). A plaiter chute (not shown) may be provided, if desired, inorder to facilitate the plaiting of the tow upon the support 26, whichlatter may be, for example, a continuously moving perforated apron. Thesupport 26 may be formed of metal or of any other suit able material.

The plaited tow 30, while resting in a relaxed state upon thecontinuously moving support, is passed through the quenching zone 32 ofthe tow quencher 12. In this zone a cooled gas, specifically cooled air,is circulated as indicated by the arrows in Fig. 1. One or more openings(not shown), as desired or as may be required, may be provided for theintake of outside air or other gas into the quenching zone. The airfilter 34 provides means for filtration of impurities from the air orother gas which is circulated through the zone. After passage throughthis filter the gas passes over the cooling coils 36 through which acold fluid medium, e. g., refrigerated brine solution or other suitablecoolant, is circulated. This cold fluid medium enters the coils 36 atinlet end 38 and leaves through outlet end 40. A suitable fan 42, e. g.,a multi-blade fan wheel or equivalent device, facilitates thecirculation of the cooling gas through the quenching zone, and over andthrough the tow during its passage through said zone while resting onthe support. The heat of the tow is imparted to the cooled gas,specifically cooled air, which is circulated through the perforated orporous movingsupport. The circulated, cooled gas sets the crimp in thetow and also reduces the moisture content of the tow, with theeconomical and practical advantages mentioned hereinbefore.

The temperature of the quenching zone 32 and the time the tow ispresenttherein are correlated so that the tow is at a temperature below120 F., preferably not higher than about 100 F., e. g., about 80-90" F.when it leaves the quenching zone and the end of the moving support, asindicated at 44, and from which it falls into a suitable chute 46. It isthen ready for further processing as has been described hereinbefore.

In a typical example air is cooled to a temperature of about 35-45 F. bypassage over the cooling coils 36, and is then circulated as illustratedin Fig. 1. The hot tow of polyacrylonitrile filamentary material iscomprised of a polymer of acrylonitrile containing, by weight, about 95%acrylonitrile and 5% methyl acrylate; and is at a temperature of about175 F. when it is plaited upon the support 26. It contains about 100% byweight of water and about 0.8% by weight of an antistatic finish. Thequenching zone 32 is about 9 feet long. The hot, plaited tow 30 iscarried through this zone, while resting on the continuously movingsupport 26, at an average rate of between about 800 and about 2000pounds per hour, based on the bone-dry weight of the tow. The quenchedtow is at an average temperature of between about F. and about F. whenit leaves the exit end of the quenching zone 32 and is at approximatelythis same temperature when it leaves the support 26 at the point 44.

It will be understood, of course, by those skilled in the art that myinvention is not limited to the processing of a mechanically hot-crimpedtow of filamentary material comprised of a copolymer of about by weightof acrylonitrile and about 5% by weight of methyl acrylate as set forthin the foregoing example. Thus, instead of using such a tow offilamentary material comprised of the aforesaid copolymer, I may use atow of filamentary material comprised of, for example, a homopolymer ofacrylonitrile or of a ternary polymer of, by weight, about 88%acrylonitrile, about 6% of vinyl acetate and about 6% of avinylpyridine, e. g., 2-methyl-5-vinylpyridine. Other acrylonitrilecopolymers (thermoplastic acrylonitrile copolymers) of which the tow maybe composed or comprised, and after being hot-crimped mechanically thenused in practicing the present invention, are acrylonitrile copolymerscontaining in the polymer molecules an average of, for example, at leastabout 35%, preferably at least about 75%, by weight of combinedacrylonitrile. Taking as an example the expression an acrylonitrilepolymer containing in the polymer molecules an average of at least about35 by weight of combined acrylonitrile, this means herein apolymerization product (homopolymer, copolymer or graft polymer ormixtures thereof) containing in the molecules thereof an average of atleast about 35% by weight of the acrylonitrile unit, which is consideredto be present in the individual polymer mole, cule as the group i lOHa-CH-CN or, otherwise stated, at least about 35% by weight of thereactant substance converted into and forming the polymerization productis acrylonitrile. The expression an acrylonitrile polymer containing inthe polymer molecules an average of at least about 75% by weight ofcombined acrylonitrile hasa similar meaning herein.

Illustrative examples of monomers which may be copolymerized withacrylonitrile to yield a polymerization product containing in thepolymer molecules an average of at least about 35 preferably at leastabout 75%, by weight of combined acrylonitrile are compounds containinga single CHFC grouping, for instance, the vinyl esters and especiallythe vinyl esters of saturated aliphatic monocarboxylic acids, e. g.,vinyl acetate, vinyl propionate, vinyl butyrate, etc.; vinyl halides, e.g., the vinyl chlorides, bromides and fluorides; allyl-type alcohols, e.g., allyl alcohol, methallyl alcohol, ethallyl alcohol, etc.; allyl,methallyl and other unsaturated monohydric alcohol esters of monobasicacids, e. g., allyl and methallyl acetates, laurates, cyanides, etc.;acrylic and alkacrylic acids (e. g., methacrylic, ethacrylic, etc.) andesters and amides of such acids (e. g., methyl, ethyl, propyl, butyl,etc., acrylates and methacrylates, acrylamide, methacrylamide, N-methyl, -ethyl, -propyl, -butyl, etc., acrylamides and methacrylamides,etc.); methacrylonitrile, ethacrylonitrile and otherhydrocarbon-substituted acrylonitriles; unsaturated aliphatichydrocarbons containing a single Ordinarily, the molecular weight(average molecular weight) of the polyacrylonitriles (homoploymeric orcopolymeric acrylonitriles) used in making the tow of filaments iswithin the range of 25,000 or 30,000 to 200,000 or 300,000 or higher,and advantageously is of the order of50,000 to 100,000, 'e. g., about70,00080,000, as calculated from a viscosity measurement of the saidpolymerization product in dimethyl tormamide using the Staudingerequation (reference: U. S. Patent No. 2,404,- 713).

The tow of polyacrylonitrile filamentary material may be produced froman acrylonitrile polymerization product by any suitable method and usingany suitable apparatus, but advantageously is produced as is describedin, for example, the copending application of Mario Sonnino, Serial No.536,479, filed September 26, 1955, now Patent No. 2,849,751, datedSeptember 2, 1958.

I claim:

1. In a continuous method of producing a tow of polyacrylonitrilefilamentary material wherein the said tow has been hot-crimpedmechanically by a tow crimper and is then continuously passed directlyfrom said tow crimper to a separate quenching zone while the crimped towis at a temperature of from about 150 F. to about- 200 F., theimprovement which consists in circulating cooled gas through saidquenching zone; laying the hot tow in a transverse, zigzag pattern andwhile it is in a relaxed state on a moving support; and passing thethusly supported, relaxed tow through said quenching zone, thetemperature of said zone and the time the tow is present therein beingcorrelated so that the tow is at a temperature below 120 F. when itleaves said zone.

2. The improvement as in claim 1 wherein the cooled gas which iscirculated in the quenching zone is cooled air.

3. The improvement as in claim 1 wherein the tow which is processed is atow of filamentary material comprised of a polymer of acrylonitrilecontaining a major proportion by weight of acrylonitrile combined in thepolymer molecule.

4. The improvement as in claim 3 wherein the polymer of acrylonitrile ofwhich the tow is comprised contains at least by weight of acrylonitrilecombined in the polymer molecule.

5. The improvement as in claim 1 in a method wherein the tow which ispassed directly from the tow crimper to the separate quenching zonecontains from about 50% to about 150% by weight of water, based on theweight of the bone-dry tow.

6. The improvement as in claim 1 wherein the temperature of thequenching zone and the time the tow is present therein are correlated sothat the tow is at a a .through said quenching zone; laying the hot towin a transverse, zigzag pattern and while it is in a relaxed state on amoving support; and passing the thusly supported, relaxed tow throughsaid quenching zone, the temperature of said zone and the time the towis present therein being correlated so that the tow is at a temperaturenot higher than about F. when it leaves said zone.

8. The improvement as in claim 7 wherein the cooled air is circulatedboth over and through the tow during its passage through said zone onsaid moving support.

References Cited in the file of this patent UNITED STATES PATENTS2,303,476 Kornegg Dec. 1, 1942 2,379,824 Mummery July 3, 1945 2,575,838Rainard Nov. 20, 1951 2,669,001 Keen Feb. 16, 1954 2,686,339 Holt Aug.17, 1954 2,715,309 Rosenstein et al Aug. 16, 1955 FOREIGN PATENTS595,634 Great Britain Dec. 11, 1947 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION February 24, 1959 Patent No. 2,874,446

William N. Sellers It is hereby certified that error appears in theprinted specification and that the said Letters of the above numberedpatent requiring correction Patent should read as corrected below.

Column 3, line 1, for "end" read and Signed and vsealed. this 30th dayof June 1959,s

(SEAL) i Attest: v

' ROBERT C. WATSON KARL H. AXLINE Attesting Ofiicer Q Commissioner ofPatents

